In elevators, there is an urgent requirement for safety gear and service brakes which reliably decelerate an elevator car of the elevator to a standstill if excessive speeds and/or uncontrolled travel movements occur.
Safety gear systems hitherto have had, for the purpose of triggering them, a mechanical speed limiter, a limiter cable, a deflection pulley with a tensioning weight and a lever structure between the limiter cable and the safety gear system.
Alternatively, a safety gear system can be triggered electrically. To do this, sensors such as e.g. travel sensors and accelerator sensors of a two-channel design detect an excessive speed of the elevator car.
Wedge-type safety gear systems are known for performing emergency braking of an elevator having a movable wedge, which can be placed in contact with a guide rail of the elevator for breaking purposes. Instead of a wedge-type safety gear system, a brake which has flat brake linings and in which the spring force is applied from a spring packet or disk spring packet which is ventilated, i.e. released, during the normal operation of the elevator can be used. EP 0648703 A1 discloses hydraulically ventilating (keeping the brake open) such a spring. A motor pump is provided for generating the hydraulic pressure. However, the motor pump with its connecting lines takes up a large amount of installation space.
There is a need for a hydraulic unit for hydraulically ventilating a brake which requires a particularly small amount of installation space.